Before some sensors are capable of making their intended measurements, they go through some form of conditioning. The time it takes a sensor to be conditioned and become capable of making measurements is often referred to as its run-in period. Run-in periods can last for as little as a few minutes to as long as a few days. The type of conditioning and run-in time required for each type or kind of sensor will vary depending on the condition of the sensor and the intended purpose and design of the sensor being used. For example, electrochemical sensors often contain electrodes at which electrochemical reactions take place, an electrolytic solution or transport matrix in which the reactions take place, and a membrane to control the access of analyte species. Examples of the types of conditions that control the length of run-in time include the time it takes for the appropriate oxidation or reduction of chemical species at the electrodes before the desired reactions to take place, the consistency of the electrolytic solution or transport matrix, and the hydration of the membrane. Regardless of the type of conditioning required for a particular sensor, a sensor sealed within a container without access to required compounds or signals cannot undergo run-in conditioning.